1. Field of the Invention
The present invention relates to a light source device used for a picture display device or the like, and more particularly to a light source device that synthesizes laser beams emitted from a plurality of semiconductor laser devices and concentrates the beams into an optical fiber in order to obtain a predetermined light output.
2. Description of the Related Art
A conventional light source device, which synthesizes laser beams emitted from a plurality of semiconductor laser devices and concentrates the beams into an optical fiber, in order to obtain a predetermined light output, is configured to include: a plurality of chip-like semiconductor lasers arranged and fixed on a heat block; collimator lens arrays provided corresponding to the semiconductor lasers; a condenser lens that concentrates collimator light flux generated by the collimator lens arrays into one optical fiber; and a box-like package that air-tightly seals these multiplexing optical systems.
According to the light source device of this kind, to concentrate laser beams emitted from the semiconductor laser devices into an optical fiber, the semiconductor laser devices, the collimator lens arrays, the condenser lens, and the optical fiber must be fixed with a predetermined positional precision in a state that inclinations of these parts precisely match with each other. To fix these parts in this manner, there is proposed a structure in which inclinations of precisely formed parts are measured by a laser automatic collimator and in this state, these parts are positioned precisely by a mechanical hand and are adhered and fixed (see, for example, Japanese Patent Application Laid-open No. 2006-284851 (Page 7 and FIG. 1)).
When a semiconductor laser device having an emission wavelength in a range of 350 to 450 nanometers is used, organic gas (out gas) components of e.g., an adhesive for fixing multiplexing optical systems are deposited on a light emitting unit and an optical member, and this deteriorates laser characteristics. To solve this problem, there is proposed a light source device in which the concentration of organic gas in a package is limited to less than 1000 parts per million (ppm), and inert gas having an oxygen concentration in a range of 1 to 100 ppm is enclosed into the package (see, for example, Japanese Patent No. 4115732 (Page 5 and FIG. 2)).
However, the conventional light source device has a problem in that, due to the above configuration, a structure for taking wires for driving the semiconductor laser out of the hermetic package becomes complicated.
The semiconductor laser device generates a large quantity of heat by emitting light, and accordingly has characteristics such that its light emitting efficiency is deteriorated by the heat and thus its lifetime is reduced, and its wavelength is shifted. Therefore, it is important to control heat radiation and the temperature thereof. However, the semiconductor laser device has a problem in that it cannot efficiently release the heat to outside from a fixed heat block to which the semiconductor laser device is fixed. Because the condenser lens and the semiconductor laser device are arranged on the same base plate, the thermal capacity of a portion whose temperature is to be controlled is large, and the cooling operation cannot be efficiently performed.